In optimized rubrene-based nanoparticle blends for photon upconversion, singlet energy collection outcompetes triplet-pair separation, not singlet fission
In optimized rubrene-based nanoparticle blends for photon upconversion, singlet energy collection outcompetes triplet-pair separation, not singlet fission
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DOI：
10.1039/d1tc02955j
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发表时间：
2021-10-19
影响因子：
6.4
通讯作者：
Clark, Jenny
中科院分区：
文献类型：
--
作者：
Bossanyi, David G.;Sasaki, Yoichi;Clark, Jenny
通过三重态-三重态湮灭上转换将近红外光子转换为可见光，为显著提高传统太阳能电池技术的效率提供了一种诱人的策略。红荧烯被广泛用作实现这种上转换的受体分子，但在固态下，单线态裂变的逆过程被认为阻碍了有效的上转换。因此，红荧烯有时以低浓度（0.5摩尔%）掺杂有单重态能量收集剂四苯基二苯并哌喃（DBP），其通过福斯特转移获得单重态能量。虽然单重态裂变是一个多步骤的过程，涉及到各种中间三重态对态，它之间的相互作用，三重态复合和单重态能量收集还没有详细的研究日期。在这里，我们使用瞬态吸收和时间分辨荧光光谱研究的动力学的单重态和三重态物种在红基于纳米粒子薄膜。引人注目的是，我们发现，从红荧烯到DBP的能量转移并不胜过通过单线态裂变形成的三重态对，尽管DBP掺杂的纳米颗粒膜的光致发光量子产率从3%增加到61%。我们在三重态融合和三重态猝灭缺陷对结晶红荧烯光致发光产率的众所周知的影响的背景下对这一令人惊讶的结果进行了合理化。
The conversion of near-infrared photons to visible light through triplet-triplet annihilation upconversion offers an enticing strategy for significantly boosting the efficiency of conventional solar cell technology. Rubrene is widely employed as the acceptor molecule for realising such upconversion, yet in the solid state, the reverse process of singlet fission is believed to hinder efficient upconversion. Consequently, rubrene is sometimes doped at low concentration (0.5 mol%) with the singlet energy collector tetraphenyldibenzoperiflanthene (DBP) which harvests singlet energy via Forster transfer. Although singlet fission is a multi-step process involving various intermediate triplet-pair states, the interplay between it, triplet recombination and singlet energy collection has not been studied in detail to date. Here we use both transient absorption and time-resolved fluorescence spectroscopy to investigate the dynamics of both singlet and triplet species in rubrene-based nanoparticle films. Strikingly, we find that energy transfer from rubrene to DBP does not outcompete the formation of triplet-pairs through singlet fission, despite the fact that DBP doping increases the photoluminescence quantum yield of the nanoparticle films from 3% to 61%. We rationalise this surprising result in the context of the well-known effects of triplet fusion and triplet-quenching defects on the photoluminescence yield of crystalline rubrene.